we are in process of identifying authoring tool for our requirements, we have below key areas which need to be achieved through the authoring tool,we are analyzing oxygen author for feasibility study against our requirements, i have few questions based on my analysis,

is there any preview mode available, so that author can view what has been created before publishing?is there any html editor plug-able into the authoring tool, so that i can do add/create below points.

is there any preview mode available, so that author can view what has been created before publishing?

No, using our Java-based SDK you can create an Oxygen plugin which contributes a custom view to Oxygen. And you can use for example JavaFX to embed a browser inside the view. But you will still need to convert the edited content in real time to HTML using your own code.

is there any html editor plug-able into the authoring tool, so that i can do add/create below points.

The Oxygen "Author" visual editing mode has support for form controls defined using specific CSS extensions. We have some samples in OXYGEN_INSTALL_DIR\samples/form-controls/.One of the possible already available form controls can be used to embed a JavaFX web browser in the Author visual editing mode: